Conductive sheet

ABSTRACT

A conductive sheet has a structure in which a conductive adhesive layer laminated on one side of a base substrate and a light-shielding insulating layer laminated on another side of the base substrate. The base substrate has a structure in which the same kind of metal layers are formed on respective sides of a resin film. The light-shielding insulating layer of the conductive sheet has a surface having a surface resistivity of 1.0×108 Ω/square or more, a gloss value of 80% or less, and an optical density of 1 or more.

TECHNICAL FIELD

The present invention relates to a conductive sheet suitable for a casewhere a display operation face of a display operation panel and a backface thereof are electrically continuous.

BACKGROUND ART

As a conventional electromagnetic wave-shielding tape, a conductivesheet having a conductive adhesive layer on one side of a foil of metalsuch as aluminum and copper has been proposed (Patent Literature 1). Inorder to prevent occurrence of short circuit due to contact of such aconductive sheet with another conductive body, or the like, apolyethylene terephthalate (PET) film is laminated as an insulatingresin layer on a side without a conductive adhesive layer of theconductive sheet to impart improvement of giving insulating propertiesto one side of the conductive sheet. By bonding a release film to theconductive adhesive layer, the handleability is improved.

In recent years, a display operation panel (i.e., touch panel) isapplied to a smartphone, a portable game console, a ticket sellingmachine, or the like, and a conductive sheet is used for electricalcontinuity between a display operation face and a back face thereof. Inorder to prevent occurrence of short circuit due to unintended contactof such a conductive sheet with another conductive body such as a metalhousing, an insulating resin film is laminated on one side to impartinsulating properties to the side. When the display operation face ofthe display operation panel and the back face are electricallycontinuous using such a conductive sheet, an attempt has been made tocover an outer edge of the display operation panel so that theinsulating resin film of the conductive sheet is outside. In this case,in order to improve quality of an image viewed through the displayoperation panel or prevent a reduction in image visibility, an attempthas been made to color the insulating resin film itself in black or forma black printing layer on the insulating resin film so that theinsulating resin film of the conductive sheet serves as a black frame.

CITATION LIST Patent Literature

Patent Literature 1: Japanese Patent Application Laid-Open No. Sho.62-227985

SUMMARY OF INVENTION Technical Problem

However, when the conductive sheet in Patent Literature 1 passes througha coater or the release film is peeled from the conductive sheet, ametal layer is likely to be plastically deformed as compared with thePET film, and the PET film is likely to be elastically deformed.Therefore, there is a problem in which the conductive sheet is likely tocurl. When the conductive sheet is bonded to the display operation panelso as to cover the outer edge of the display operation panel, thefollowability of the conductive sheet to a step of a bonding portion ora shape of a corner is not sufficient. Therefore, there are alsoproblems in which the conductive sheet is likely to be peeled andnecessary shape retentivity is not achieved.

An object of the present invention is to solve the above-describedproblems in the conventional techniques, and to hardly generate curl ina conductive sheet, and impart good shape stability and shapefollowability to the conductive sheet obtained by laminating aconductive adhesive layer on one side of a base substrate and laminatinga light-shielding insulating layer on another side of the basesubstrate.

Solution to Problem

The present inventor has found that when a layered body in which thesame kind of metal layers are laminated on respective sides of a resinfilm is used as a base substrate that is a center part of a conductivesheet in a thickness-wise direction, the object can be achieved. Thus,the present invention has been completed.

Specifically, the present invention provides a conductive sheet having abase substrate, a conductive adhesive layer laminated on one side of thebase substrate and a light-shielding insulating layer laminated onanother side of the base substrate, wherein the base substrate has astructure in which the same kind of metal layers are formed onrespective sides of a resin film.

In this case, as a level of insulating properties of a surface of thelight-shielding insulating layer of the conductive sheet, the surfaceresistivity is preferably 1.0×10⁸ Ω/square or more. As a level oflight-shielding properties, the gloss value is preferably 800 or lessand the optical density is preferably 1 or more.

The present invention further provides an image display module having: adisplay operation panel in which a top electrode provided on an outeredge of a surface of the display operation panel and a back electrodeprovided on an outer edge of a back face are connected via theconductive sheet of the present invention that is disposed so as tosurround the outer edge of the display operation panel; and an imagedisplay panel that is operated by the display operation panel.

Advantageous Effects of Invention

In the conductive sheet of the present invention having a basesubstrate, a conductive adhesive layer laminated on one side of a basesubstrate and a light-shielding insulating layer laminated on anotherside of the base substrate, a substrate having a structure in which thesame kind of metal layers are formed on respective sides of a resin filmis used as the base substrate. Therefore, even when a tension is appliedto the conductive sheet, generation of curl can be largely suppressed.This is because the metal layers on respective sides of the resin filmshow the same coefficients of extension. Further, since the metal layersare disposed on respective sides of the resin film, the sheet can bebonded with shape followability that is good for a changed shape such asa curved surface and a refracted part (corner), and the shaperetentivity is excellent.

When the level of insulating properties of the surface of thelight-shielding insulating layer of the conductive sheet is a surfaceresistivity of 1.0×10⁸ Ω/square or more, occurrence of short circuit dueto contact with another conductive body can be suppressed. When thelevel of light-shielding properties is set such that the gloss valuethereof is 80% or less and the optical density thereof is 1 or more, ablack mat frame can be provided on an outer edge of a display operationpanel, and the visibility of an image observed through the displayoperation panel can be largely improved.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a cross-sectional view of a conductive sheet of the presentinvention.

FIG. 2 is a cross-sectional view of a conductive sheet of the presentinvention.

FIG. 3 is a cross-sectional view of a conductive sheet of the presentinvention.

FIG. 4 illustrates image display modules (via a respective sectionalview of IDM in which the individual components are not drawn to scale)in accordance with various embodiments (EMBODIMENT 1, EMBODIMENT 2, andEMBODIMENT 3) of the present invention.

FIG. 5 illustrates image display modules (via a respective sectionalview of IDM in which the individual components are not drawn to scale)in accordance with various embodiments (EMBODIMENT 1, EMBODIMENT 2,EMBODIMENT 3, and EMBODIMENT 4) of the present invention.

FIG. 6 illustrates image display modules (via a respective sectionalview of IDM in which the individual components are not drawn to scale)in accordance with various embodiments (EMBODIMENT 1, EMBODIMENT 2, andEMBODIMENT 3) of the present invention.

DESCRIPTION OF EMBODIMENTS

Hereinafter, the conductive sheet of the present invention will bedescribed in detail with reference to the drawings.

FIG. 1 is a cross-sectional view of a conductive sheet 100 of thepresent invention. This conductive sheet 100 has a structure in which aconductive adhesive layer 20 is formed on one side of a base substrate10 and a light-shielding insulating layer 30 is formed on another side.

<Base Substrate>

In the conductive sheet 100 of the present invention, the base substrate10 is characterized by having a structure in which the same kind ofmetal layers 2 and 3 are laminated on respective sides of a resin film1. Therefore, generation of curl in the conductive sheet can be largelysuppressed, and good followability and shape stability can be impartedto the conductive sheet.

As the resin film 1 constituting the base substrate 10, a resin filmused as a base film of the conductive sheet can be preferably used.Examples of such a resin film may include polyester films, polyolefinfilms, polyamide films, polyurethane films, and polystyrene films. Amongthem, the polyester films, and especially a polyethylene terephthalatefilm can be preferably used from the viewpoints of availability,mechanical strength, heat resistance, cost, and rust prevention.

In order to retain the mechanical strength of the conductive sheet, andachieve good shape followability and shape stability, the thickness ofthe resin film 1 constituting the base substrate 10 is preferably 5 to20 μm, and more preferably 7 to 15 μm.

As the metal layers 2 and 3 constituting the base substrate 10, a metallayer used as a conventional conductive sheet can be preferably used.For such metal layers 2 and 3, aluminum, copper, nickel, gold, silver,and the like may be exemplified. Among them, aluminum can be preferablyused from the viewpoints of availability, mechanical strength, heatresistance, cost, and rust prevention.

In order to retain the mechanical strength of the conductive sheet, andachieve good shape followability and shape stability, the thickness ofeach of the metal layer 2 on a side of the conductive adhesive layer 20and the metal layer 3 on a side of the light-shielding insulating layer30 is preferably 5 to 20 and more preferably 7 to 15 μm.

The ratio [Mt1]:[Bt]:[Mt2] of the thickness [Mt1] of the metal layer 2on the conductive adhesive layer 20 side, the thickness [Bt] of theresin film 1, and the thickness [Mt2] of the metal layer 3 on thelight-shielding insulating layer 30 side is preferably 0.25 to 4:1:0.25to 4, and more preferably 0.4 to 2.4:1:0.4 to 2.4 from the viewpoints ofbalance of shape followability and shape retentivity.

The metal layers 2 and 3 can be formed on the resin film 1 by aconventional method. Examples of the method may include a method oflaminating metal foils as metal layers on the resin film 1 via anadhesive layer 40 that is formed from a dry adhesive such as apolyester-based adhesive and a polyurethane-based adhesive that containan isocyanate-based cross-linker, a method of forming the metal layers 2and 3 on respective sides of the resin film 1 by electroless metalplating, followed by electrolytic metal plating, and a method oflaminating the metal layers 2 and 3 on respective sides of the resinfilm 1 by a vacuum deposition method. Among them, the method oflaminating the metal layers via the adhesive layer can be preferablyapplied in terms of high mass productivity and low production cost.

When the linear expansion coefficient [ppm/° C.] of the resin film 1constituting the base substrate 10 is too large, curl is likely to begenerated. When it is too small, a layered structure becomes unstable ina heat environment. From this trend, delamination may occur. Therefore,the linear expansion coefficient of the resin film 1 is preferably 15 to100 ppm/° C., and more preferably 20 to 70 ppm/° C.

The linear expansion coefficient [ppm/° C.] of the metal layers 2 and 3is preferably 12 to 25 ppm/° C., and more preferably 16 to 23 ppm/° C.from the viewpoint of stability of the layered structure with the resinfilm 1.

When the difference between the linear expansion coefficient of theresin film 1 and the linear expansion coefficient of the metal layers 2and 3 is too large, curl tends to be easily generated. Therefore, thedifference is preferably 40 ppm/° C. or less, and more preferably 25ppm/° C. or less.

When the modulus of elongation [GPa] of the resin film 1 constitutingthe base substrate 10 in accordance with JIS K7113 is too small, theconductive sheet tends to easily curl. When it is too large, the shapefollowability tends to be deteriorated. Therefore, the modulus ofelongation of the resin film 1 is preferably 0.3 to 15 GPa, and morepreferably 2 to 7 GPa.

When the modulus of elongation [GPa] of the metal layers 2 and 3 inaccordance with JIS K7113 is too small, the conductive sheet tends toeasily curl. When it is too large, the shape followability tends to bedeteriorated. Therefore, the modulus of elongation of the metal layers 2and 3 is preferably 45 to 200 GPa, and more preferably 75 to 130 GPa.

When the difference of modulus of elongation in accordance with JISK7113 between the resin film 1 and the metal layers 2 and 3, whichconstitute the base substrate 10, is too large, curl tends to be easilygenerated. Therefore, the difference is preferably 100 GPa or less, andmore preferably 80 GPa or less.

<Light-Shielding Insulating Layer>

The light-shielding insulating layer 30 constituting the conductivesheet 100 of the present invention is a layer of impartinglight-shielding properties and insulating properties to the conductivesheet 100. Herein, when the level of insulating properties of thesurface of the light-shielding insulating layer 30 of the conductivesheet 100 is too low, short circuit may occur. Therefore, the surfaceresistivity is preferably 1.0×10⁸ Ω/square or more, and more preferably1.0×10¹⁰ Ω/square or more.

In order to improve the visibility of an image, as the level oflight-shielding properties of the light-shielding insulating layer 30,the gloss value in accordance with JIS 28741 (incidence angle: 60° C.)is preferably 80% or less, and more preferably 40% or less, and theoptical density in accordance with JIS K7605 is preferably 1 or more,more preferably 1.2 or more, and further preferably 1.4 or more.

When the thickness of the light-shielding insulating layer 30 is toosmall, intended optical characteristics tend to be deteriorated. When itis too large, a crack tends to be generated. Therefore, the thickness ofthe light-shielding insulating layer 30 is preferably 3 to 15 and morepreferably 5 to 11 μm.

Such a light-shielding insulating layer 30 may have variousconfigurations in which the surface resistivity, gloss value, andoptical density of the surface fall within the above-described ranges.Examples thereof may include a configuration that is a black resin layerof single layer that is formed from an insulating resin colored by ablack colorant, as shown in FIG. 1, and a configuration that includes ablack resin layer 30 a formed from an insulating resin colored by ablack colorant, and an insulating primer layer 30 b or a mat varnishlayer 30 c that is formed on one side thereof, as shown in FIG. 2 or 3.

Examples of the insulating resin in the black resin layer constitutingthe light-shielding insulating layer 30 may include polyethylene,polypropylene, ethylene-α-olefin copolymers such as ethylene-propylenecopolymers, polymethyl pentene, polyvinyl chloride, polyvinylidenechloride, polyvinyl acetate, ethylene-vinyl acetate copolymers,polyvinyl alcohol, polyvinyl acetal, fluorine-containing polymers suchas polyvinylidene fluoride and polytetrafluoroethylene, polyethyleneterephthalate, polybutylene terephthalate, polyethylene naphthalate,polystyrene, polyacrylonitrile, styrene-acrylonitrile copolymers,acrylonitrile-butadiene-styrene copolymer (ABS) resins,polyphenylene-ether copolymer (PPE) resins, modified PPE resins,aliphatic polyamides, aromatic polyamides, polyimide, polyamide imide,polymethacrylic acid, polymethacylic acid esters such as polymethylmethacrylate, polyacrylic acids, polycarbonate, polyphenylene sulfide,polysulfone, polyether sulfone, polyether nitrile, polyether ketone,polyketone, liquid crystal polymers, silicone resins, and thermoplasticresins such as an ionomer. Further, examples thereof may includestyrene-butadiene block copolymers and hydrogenated products thereof,styrene-isoprene block copolymers and hydrogenated products thereof, andthermoplastic elastomers such as styrenic thermoplastic elastomers,olefinic thermoplastic elastomers, vinyl chloride-based thermoplasticelastomers, polyester-based thermoplastic elastomers, polyurethane-basedthermoplastic elastomers, and polyamide-based thermoplastic elastomers.In addition, examples thereof may include cross-linked rubbers, epoxyresins, phenolic resins, polyimide resins, unsaturated polyester resins,and diallyl phthalate resins. Specific examples of the cross-linkedrubber may include thermosetting resins such as natural rubbers, acrylicrubbers, butadiene rubbers, isoprene rubbers, styrene-butadienecopolymer rubbers, nitrile rubbers, hydrogenated nitrile rubbers,chloroprene rubbers, ethylene-propylene copolymer rubbers, chlorinatedpolyethylene rubbers, chlorosulfonated polyethylene rubbers, butylrubbers, halogenated butyl rubbers, fluoro rubbers, urethane rubbers,and silicone rubbers. Light-curable resins can be also applied.

Examples of the black colorant may include known black dyes and blackpigments, such as aniline black, carbon black, and black titanium oxide.When the average particle diameter of the colorant is too small, aprobability in which it is difficult that the colorant is uniformlymixed in the insulating resin during production tends to increase. Whenit is too large, the smoothness of the light-shielding insulating layer30 tends to decrease. Therefore, the average particle diameter of thecolorant is preferably 10 to 500 nm, and more preferably 50 to 100 nm.When the content of the black colorant in the black resin layer is toosmall, intended optical characteristics tend not to be achieved. When itis too large, adhesion to an adjacent layer may be reduced or the resinlayer may be separated. Therefore, the content of the black colorant inthe black resin layer is preferably 10 to 40% by mass, and morepreferably 15 to 30% by mass.

Examples of the insulating primer layer 30 b shown in FIG. 2 may includea layer in which fillers such as silica are mixed in the insulatingresin exemplified in the black resin layer, if necessary, to preventblocking.

When the thickness of the insulating primer layer 30 b is too small,intended insulating properties tend not to be achieved. When it is toolarge, intended shape retentivity tends not to be achieved. Therefore,the thickness of the insulating primer layer 30 b is preferably 2 to 10μm, and more preferably 3 to 7 μm.

Examples of the mat varnish layer 30 c shown in FIG. 3 may include afilm formed by mixing fillers having an average particle diameter of 0.1to 10 μm, such as silica, barium sulfate, calcium carbonate,polyethylene beads, polystyrene beads, and benzoguanamine beads,preferably in a content of 30 to 80% by mass, in the insulating resinexemplified in the black resin layer to achieve good balance between apreferred mat appearance and good coating film strength.

When the thickness of the mat varnish layer 30 c is too small, intendedinsulating properties tend not to be achieved. When it is too large,intended shape retentivity and optical characteristics tend not to beachieved. Therefore, the thickness of the mat varnish layer 30 c ispreferably 2 to 10 and more preferably 3 to 7 μm.

When the light-shielding insulating layer 30 is a black resin layer ofsingle layer as shown in FIG. 1, it is preferable that aniline black beused as the black colorant. This is because the black colorant itself isinsulative. When the light-shielding insulating layer 30 has a two-layerstructure as shown in FIG. 2 or 3, aniline black may be used as theblack colorant of the black resin layer 30 a. However, carbon black thatis conductive may be used within a range not impairing the effects ofthe present invention. This is because there are the insulating primerlayer 30 b and the mat varnish layer 30 c that secure insulatingproperties.

<Conductive Adhesive Layer>

As the conductive adhesive layer 20 constituting the conductive sheet100, a conductive adhesive layer of the conventional conductive sheetcan be used. Examples thereof may include a film formed by mixingconductive particles such as carbon black and metal particles in anamount sufficient to achieve such conductivity that the surfaceresistivity is 500 mΩ/square or less in the insulating resin exemplifiedin the black resin layer.

When the thickness of the conductive adhesive layer 20 is too small,intended adhesive properties tend not to be achieved. When it is toolarge, intended electrical continuity tends not to be achieved.Therefore, the thickness of the conductive adhesive layer 20 ispreferably 10 to 35 μm, and more preferably 15 to 25 μm.

<Production of Conductive Sheet>

The conductive sheet of the present invention can be produced through aknown procedure. For example, a dry adhesive such as a urethane-basedadhesive containing an isocyanate curing agent is applied to one side ofa resin film such as a PET film, and a metal layer such as aluminum foilis laminated. After that, a dry adhesive is applied to another side, anda metal layer is laminated in the same manner. Thus, a base substratehaving the metal layers laminated on respective sides is formed.Subsequently, a coating for a conductive adhesive layer is applied to arelease sheet, and dried to form a conductive adhesive layer, and thebase substrate is laminated on the conductive adhesive layer. Next, ablack ink for formation of a black resin layer is applied to the basesubstrate, and dried to form a light-shielding insulating layer. Thus,the conductive sheet in FIG. 1 is obtained.

The conductive sheets in FIGS. 2 and 3 can be produced basically in thesame manner as in a case of the conductive sheet in FIG. 1 except that ablack resin layer, a mat varnish layer, and an insulating primer layerare each formed by applying and drying.

The conductive sheet of the present invention can be preferably appliedto an image display module in which a portion to be electricallyconnected is disposed in a rough plane as illustrated in the embodiments(EMBODIMENT 1, EMBODIMENT 2, and EMBODIMENT 3) shown in FIG. 4, or animage display module in which portions to be electrically connected aredisposed on respective different planes as illustrated in theembodiments (EMBODIMENT 1, EMBODIMENT 2, EMBODIMENT 3, and EMBODIMENT 4)shown in FIG. 5.

Examples of the former may include an image display module in which adisplay panel such as a notebook computer is disposed so as to beconnected to a substrate separately provided across any bend portion andstep using the conductive sheet. The image display module illustrated bythis notebook computer is also part of the invention of the presentapplication.

Examples of the latter may include an image display module asillustrated in the embodiments (EMBODIMENT 1, EMBODIMENT 2, andEMBODIMENT 3) shown in FIG. 6 formed by combining a display operationpanel, such as a touch panel, in which a top electrode provided on anouter edge of the surface of the display operation panel and a backelectrode provided on an outer edge of a back face are connected anddisposed so as to surround the outer edge of the display operation panelwith the conductive sheet with an image display panel to be operated,such as a liquid-crystal display panel. The image display module is alsopart of the invention of the present application.

EXAMPLES Example 1

3 g/m² (in terms of dry coating amount) of polyester resin (UE3220,available from UNITIKA LTD.) using an isocyanate-based curing agent(CORONATE L, available from Nippon Polyurethane Industry Co., Ltd.) wasapplied to one side of a PET film (Mylar, available from Teijin DuPontFilms Japan Limited) with a thickness of 5 m, and a soft aluminum foil(1030N-0, available from Nippon Foil Mfg. Co., Ltd.) with a thickness of7 μm was laminated thereon. A soft aluminum foil (1030N-0, availablefrom Nippon Foil Mfg. Co., Ltd.) with a thickness of 7 μm was laminatedon another side of the PET film in the same manner to form a basesubstrate.

A black conductive adhesive (acrylic adhesive containing 10% by mass ofcarbon black) was applied to a release PET film so that the driedthickness was 25 μm, and dried to form a black conductive adhesivelayer. The base substrate previously formed was laminated on the blackconductive adhesive layer.

Subsequently, a black insulating ink (ink (available from DexerialsCorporation) obtained by dispersing aniline black (available from TokyoShikizai Industry Co., Ltd.) in a polyester resin (VYLON 200, availablefrom Toyobo Co., Ltd.)) was applied to the base substrate so that thedried thickness was 3 μm, and dried to form a light-shielding insulatinglayer. Thus, a conductive sheet having the configuration shown in Table1 was obtained.

Example 2

A conductive sheet having a configuration shown in Table 1 was obtainedby repeating the same operations as in Example 1 except that a PET film(E5100, available from Toyobo Co., Ltd.) with a thickness of 12 μm wasused instead of the PET film with a thickness of 5 μm in the basesubstrate.

Example 3

A conductive sheet having a configuration shown in Table 1 was obtainedby repeating the same operations as in Example 1 except that a layeredbody of an insulating primer layer (polyester resin (VYLON200, availablefrom Toyobo Co., Ltd.)) with a thickness of 3 μm from a side of the basesubstrate and a black carbon black ink layer (ink (available fromDexerials Corporation) obtained by dispersing carbon black (MA8,available from Mitsubishi Chemical Corporation) in a polyester resin(VYLON 200, available from Toyobo Co., Ltd.)) formed on the layer wasused as the light-shielding insulating layer.

Example 4

A conductive sheet having a configuration shown in Table 1 was obtainedby repeating the same operations as in Example 1 except that a layeredbody of a black carbon black ink layer with a thickness of 3 μm (ink(available from Dexerials Corporation) obtained by dispersing carbonblack (MA8, available from Mitsubishi Chemical Corporation) in apolyester resin (VYLON 200, available from Toyobo Co., Ltd.)) and a matvarnish layer (LG 6620, available from Tokyo Printing Ink Mfg. Co.,Ltd.) with a thickness of 3 μm from a side of the base substrate wasused as the light-shielding insulating layer.

Comparative Example 1

A conductive sheet having a configuration shown in Table 1 was obtainedby repeating the same operations as in Example 1 except that a blackcarbon black ink layer with a thickness of 3 μm (ink (available fromDexerials Corporation) obtained by dispersing carbon black (MA8,available from Mitsubishi Chemical Corporation) in a polyester resin(VYLON 200, available from Toyobo Co., Ltd.)) was used as thelight-shielding insulating layer.

Comparative Example 2

A conductive sheet having a configuration shown in Table 1 was obtainedby repeating the same operations as in Comparative Example 1 except thatthe urethane-based adhesive used in Example 1 was applied to the metallayer of the base substrate before formation of the black carbon blackink layer, and a PET film (Mylar, available from Teijin DuPont FilmsJapan Limited) with a thickness of 5 μm was laminated thereon, and thenthe black carbon black ink layer was formed.

Comparative Example 3

A conductive sheet having a configuration shown in Table 1 was obtainedby repeating the same operations as in Comparative Example 2 except thata PET film (E5100, available from Toyobo Co., Ltd.) with a thickness of12 μm was used instead of the PET film with a thickness of 5 μminterposed between aluminum foils in the base substrate.

Comparative Example 4

A conductive sheet having a configuration shown in Table 1 was obtainedby repeating the same operations as in Comparative Example 1 except thata PET film with a thickness of 5 μm on one side of which the softaluminum foil laminated via an adhesive used in Example 1 was used asthe base substrate, and a layered body of a black carbon black ink layer(ink (available from Dexerials Corporation) obtained by dispersingcarbon black (MA8, available from Mitsubishi Chemical Corporation) in apolyester resin (VYLON 200, available from Toyobo Co., Ltd.)) wasdirectly used on a side of the base substrate where no soft aluminumfoil was laminated.

Comparative Example 5

A conductive sheet having a configuration shown in Table 1 was obtainedby repeating the same operations as in Comparative Example 4 except thata PET film (E5100, available from Toyobo Co., Ltd.) with a thickness of12 μm was used instead of the PET film with a thickness of 5 μm in thebase substrate.

Comparative Example 6

A conductive sheet having a configuration shown in Table 1 was obtainedby repeating the same operations as in Comparative Example 4 except thata conductive non-woven fabric-enhanced adhesive film (Sui-80-M30,available from Seiren Co., Ltd.) with a thickness of 30 μm was laminatedinstead of the formation of the conductive adhesive layer on the releasePET film.

Comparative Example 7

A conductive sheet having a configuration shown in Table 1 was obtainedby repeating the same operations as in Comparative Example 6 except thata PET film (E5100, available from Toyobo Co., Ltd.) with a thickness of12 μm was used instead of the PET film with a thickness of 5 μminterposed between aluminum foils in the base substrate.

<Evaluation>

“Curl characteristics,” “shape retentivity,” “shape followability(repulsion),” “insulating properties (surface resistivity),” and“light-shielding properties (gloss value and optical density)” in theresulting conductive sheets were tested and evaluated, as describedbelow. The obtained results are shown in Table 1.

“Curl Characteristics”

In a testing sample in which the conductive sheet was cut into a stripwith a width of 15 mm and a length of 150 mm, a release sheet on a sideof the conductive adhesive layer was peeled in a direction of 180° at arate of 1,000 mm/sec, and resulting curl was visually observed. A casewhere the resulting curl is within one rotation is judged to be good,and a case where the curl exceeds one rotation is judged to be poor.

“Shape Retentivity”

In a testing sample in which the conductive sheet was cut into a stripwith a width of 15 mm and a length of 50 mm, a release sheet on a sideof the conductive adhesive layer was peeled in a direction of 180° at arate of 1,000 mm/sec, and bent at 90° at a center of the sample on aside of the light-shielding insulating layer. A shape to be retained inthis state for 10 seconds was visually observed. A case where the shapeis retained is judged to be good, and a case where the shape is notretained is judged to be poor.

“Shape Followability (Repulsion)”

In a testing sample in which the conductive sheet was cut into arectangle with a length of 15 mm and a width of 10 mm, a release sheeton a side of the conductive adhesive layer was removed. A long side ofthe sample was bonded to an aluminum plate so that a portion with athickness of 1 mm of the aluminum plate was surrounded and a 1-mm edgeon a surface of the aluminum plate was covered. The rest was bent at 90°and bonded to a back face of the aluminum plate. After the sample wasleft in an environment of 80° C. and 95% RH for 72 hours, the presenceor absence of peeling was visually observed. A case where peeling doesnot occur is judged to be good, and a case where peeling occurs isjudged to be poor.

“Insulating Properties (Surface Resistivity)”

The surface resistance of a surface of the light-shielding insulatinglayer of the conductive sheet was measured with a resistivity meter(Hiresta, manufactured by Mitsubishi Chemical Analytech, Co., Ltd.). Thesurface resistivity is required to be 1×10⁸ Ω/square or more inpractical terms.

“Light-Shielding Properties (Gloss Level and Optical Density)”

The gloss value of the light-shielding insulating layer surface of theconductive sheet was measured with a gloss value meter (Gloss CheckerIG-320, manufactured by Horiba, Ltd.) in accordance with JIS 28741(angle of incidence: 60°). The gloss value is required to be 80% or lessin practical terms. The optical density of the light-shieldinginsulating layer surface was measured with an optical density meter(reflection density meter RT924, manufactured by Macbeth) in accordancewith JIS K7605. The optical density is required to be 1.4 or more inpractical terms. A case where both the performances are satisfied isjudged to be good.

For conductivity of the conductive adhesive layer of the conductivesheet in each of Examples 1 to 4 and Comparative Examples 1 to 5 and theconductive non-woven fabric-enhanced adhesive film in each ofComparative Examples 6 and 7, a sample cut into a strip of 100×25 mm wasbonded to end portions of two copper foils (1×25×100 mm) that weredisposed in parallel at an interval of 50 mm so as to be bridged, andthe resistance value between the two copper foils was measured with anelectrical resistance meter (Milliohm Meter 4332B, manufactured byAgillent). The results of all the samples represent a value as very lowas 50 to 60 mΩ, which is largely less than 500 mΩ.

TABLE 1 EXAMPLE COMPARATIVE EXAMPLE 1 2 3 4 1 2 LIGHT-SHIELDING BLACKBLACK BLACK MAT BLACK BLACK INSULATING LAYER INSULATING INSULATINGCARBON VARNISH CARBON CARBON INK INK BLACK INK BLACK INK BLACK INKINSULATING BLACK PRIMER CARBON BLACK INK BASE SUBSTRATE — — — — — 5-μmPET 7-μm Al FOIL 7-μm Al FOIL 7-μm Al FOIL 7-μm Al FOIL 7-μm Al FOIL7-μm Al FOIL 5-μm PET 12-μm PET 5-μm PET 5-μm PET 5-μm PET 5-μm PET 7-μmAl FOIL 7-μm Al FOIL 7-μm Al FOIL 7-μm Al FOIL 7-μm Al FOIL 7-μm Al FOILCONDUCTIVE 25-μm THICK 25-μm THICK 25-μm THICK 25-μm THICK 25-μm THICK25-μm THICK ADHESIVE LAYER BLACK BLACK BLACK BLACK BLACK BLACKCONDUCTIVE CONDUCTIVE CONDUCTIVE CONDUCTIVE CONDUCTIVE CONDUCTIVEADHESIVE ADHESIVE ADHESIVE ADHESIVE ADHESIVE ADHESIVE CURL GOOD GOODGOOD GOOD GOOD POOR CHARACTERISTICS SHAPE RETENTIVITY GOOD GOOD GOODGOOD GOOD GOOD SHAPE GOOD GOOD GOOD GOOD GOOD GOOD FOLLOWABILITYINSULATING 3.0 × 10⁸ 1.9 × 10⁹ 1.0 × 10⁸ 1.0 × 10¹¹ <1.0 × 10⁶ 5.7 × 10⁸PROPERTIES (Ω/Sq.) LIGHT-SHIELDING 30.0 30.0 40.0 10.0 40.0 40.0PROPERTIES GLOSS VALUE (%) OPTICAL DENSITY 1.3 1.3 1.4 1.3 1.4 1.4COMPARATIVE EXAMPLE 3 4 5 6 7 LIGHT-SHIELDING BLACK BLACK BLACK BLACKBLACK INSULATING LAYER CARBON CARBON CARBON CARBON CARBON BLACK INKBLACK INK BLACK INK BLACK INK BLACK INK BASE SUBSTRATE 5-μm PET — — — —7-μm AIFOL — — — — 12-μm PET 5-μm PET 12-μm PET 5-μm PET 12-μm PET 7-μmAl FOIL 7-μm Al FOIL 7-μm Al FOIL 7-μm Al FOIL 7-μm Al FOIL CONDUCTIVE25-μm THICK 25-μm THICK 25-μm THICK 30-μm THICK 30-μm THICK ADHESIVELAYER BLACK BLACK BLACK CONDUCTIVE CONDUCTIVE CONDUCTIVE CONDUCTIVECONDUCTIVE NON-WOVEN NON-WOVEN ADHESIVE ADHESIVE ADHESIVE FABRIC-FABRIC- ENHANCED ENHANCED ADHESIVE ADHESIVE FILM FILM CURL POOR POORPOOR GOOD GOOD CHARACTERISTICS SHAPE RETENTIVITY GOOD POOR POOR POORPOOR SHAPE POOR GOOD GOOD POOR POOR FOLLOWABILITY INSULATING 6.4 × 10⁸6.4 × 10⁸ 6.5 × 10⁸ 7.0 × 10⁸ 6.5 × 10⁸ PROPERTIES (Ω/Sq.)LIGHT-SHIELDING 40.0 40.0 40.0 40.0 40.0 PROPERTIES GLOSS VALUE (%)OPTICAL DENSITY 1.4 1.4 1.4 1.4 1.4

In all evaluation items of the conductive sheets in Examples 1 to 4,good results are obtained.

In contrast, in the conductive sheet in Comparative Example 1, a blackinsulating ink was not used, and the light-shielding insulating layerwas formed using a black carbon black ink exhibiting conductivity.Therefore, the surface resistivity is low and insulating propertiesexhibited are not satisfied in practical terms.

In the conductive sheet in Comparative Example 2, a black insulating inkwas not used, and the light-shielding insulating layer was formed usinga black carbon black ink, but the insulating PET film was disposed underthe black carbon black ink layer. Therefore, good insulating propertiesare exhibited, but symmetry in the thickness-wise direction of the basesubstrate is lost. Accordingly, a problem of curl characteristicsarises.

In the conductive sheet in Comparative Example 3, the thickness of theresin film in the base substrate of the conductive sheet in ComparativeExample 2 was increased from 5 μm to 12 μm. Therefore, symmetry in thethickness-wise direction of the base substrate is lower than that inComparative Example 2, and as a result, a problem of shape followabilityarises.

In all the conductive sheets in Comparative Examples 4 and 5, the basesubstrate in which the aluminum foil was laminated only on one side wasused. Therefore, the shape followability is good, but problems of curlcharacteristics and shape retentivity arise.

In the conductive sheets in Comparative Examples 6 and 7, the non-wovenfabric-enhanced adhesive film was used as the conductive adhesive layer.Therefore, a problem of curl characteristics arises. However, since thebase substrate in which the aluminum foil was laminated only on one sidewas used, problems of shape retentivity and shape followability arise.

INDUSTRIAL APPLICABILITY

In the conductive sheet of the present invention obtained by laminatinga conductive adhesive layer on one side of a base substrate andlaminating a light-shielding insulating layer on another side of thebase substrate, a substrate having a structure in which the same kind ofmetal layers are formed on respective sides of a resin film is used asthe base substrate. Therefore, even when a tension is applied to theconductive sheet, generation of curl can be largely suppressed. This isbecause the metal layers on respective sides of the resin film show thesame coefficients of extension. Further, the sheet can be bonded withshape followability that is good for a changed shape such as a curvedsurface and a refracted part (corner), and the shape retentivity isexcellent. Accordingly, the conductive sheet of the present invention isuseful in production of an image display module in which a portion to beelectrically connected is disposed in a rough plane, or an image displaymodule in which portions to be electrically connected are disposed onrespective different planes.

REFERENCE SIGNS LIST

-   -   1 resin film    -   2 metal layer on the conductive adhesive layer side    -   3 metal layer on the light-shielding insulating layer side    -   10 base substrate    -   20 conductive adhesive layer    -   30 light-shielding insulating layer    -   30 a black resin layer    -   30 b insulating primer layer    -   30 c mat varnish layer    -   100 conductive sheet

The invention claimed is:
 1. A conductive sheet comprising a basesubstrate, a conductive adhesive layer laminated on one side of the basesubstrate and a light-shielding insulating layer laminated on anotherside of the base substrate, wherein the base substrate has a structurein which the same kind of metal layers are formed on respective sides ofa resin film, where the structure of the base substrate is formed bylaminating metal foils on the respective sides of the resin film via anadhesive layer, the light-shielding insulating layer of the conductivesheet has a surface having a surface resistivity of 1.0×10⁸ Ω/square ormore, and the conductive adhesive layer of the conductive sheet has asurface having a surface resistivity of 500 mΩ/square or less, and theconductive sheet exhibits a curl characteristic in that when theconductive sheet further comprises a release sheet on a side of theconductive adhesive layer, and when the conductive sheet is cut into asample strip with a width of 15 mm and a length of 150 mm, peeling therelease sheet from the sample strip in a direction of 180° results in acurl of the sample strip of less than one rotation.
 2. The conductivesheet according to claim 1, wherein the light-shielding insulating layerof the conductive sheet has a gloss value of 80% or less, and an opticaldensity of 1 or more.
 3. The conductive sheet according to claim 1,wherein the light-shielding insulating layer of the conductive sheet hasa surface having a surface resistivity of 1.0×10¹⁰ Ω/square or more, agloss value of 40% or less, and an optical density of 1.2 or more. 4.The conductive sheet according to claim 1, wherein the resin filmconstituting the base substrate has a linear expansion coefficient of 15to 100 ppm/° C. and the metal layer has a linear expansion coefficientof 12 to 25 ppm/° C.
 5. The conductive sheet according to claim 4,wherein a difference between the linear expansion coefficient of theresin film and the linear expansion coefficient of the metal layersconstituting the base substrate is 40 ppm/° C. or less.
 6. Theconductive sheet according to claim 1, wherein the resin filmconstituting the base substrate has a modulus of elongation (inaccordance with JIS K7113) is 0.3 to 15 GPa, and the metal layer has amodulus of elongation of 45 to 200 GPa.
 7. The conductive sheetaccording to claim 6, wherein a difference between the modulus ofelongation (in accordance with JIS K7113) of the resin film and themodulus of elongation of the metal layers constituting the basesubstrate is 100 GPa or less.
 8. The conductive sheet according to claim1, wherein the resin film, the metal layer on a side of the conductiveadhesive layer, and the metal layer on a side of the light-shieldinginsulating layer, which constitute the base substrate, are each 5 to 20μm in a vertical thickness of the resin film.
 9. The conductive sheetaccording to claim 8, wherein a ratio [Mt1]:[Bt]:[Mt2] of a thickness[Mt1] of the metal layer on the side of the conductive adhesive layer, athickness [Bt] of the resin film, and a thickness [Mt2] of the metallayer on the side of the light-shielding insulating layer is one havingvalues in the range of 0.25 to 4:1:0.25 to 4 in a vertical thickness ofthe resin film.
 10. The conductive sheet according to claim 1, whereinthe light-shielding insulating layer is a black resin layer that isformed from an insulating resin colored by a black colorant.
 11. Theconductive sheet according to claim 10, wherein the black colorant isaniline black.
 12. The conductive sheet according to claim 1, whereinthe light-shielding insulating layer comprises a black resin layer thatis formed from an insulating resin colored by a black colorant, and aninsulating primer layer or a mat varnish layer formed on at least oneside thereof.
 13. The conductive sheet according to claim 12, whereinthe black colorant is carbon black.
 14. An image display in which aportion to be electrically connected is disposed in a rough plane and isconnected by the conductive sheet according to claim
 1. 15. An imagedisplay in which portions to be electrically connected are disposed onrespective different planes and are connected by the conductive sheetaccording to claim
 1. 16. An image display comprising: a displayoperation panel in which a top electrode provided on an outer edge of asurface of the display operation panel and a back electrode provided onan outer edge of a back face are connected via the conductive sheetaccording to claim 1 that is disposed so as to surround the outer edgeof the display operation panel; and an image display panel that isoperated by the display operation panel.
 17. An image display in whichthe conductive sheet according to claim 1 is bonded to the image displayso as to surround an outer edge of at least one constituent memberthereof.
 18. A conductive sheet comprising a base substrate, aconductive adhesive layer laminated on one side of the base substrateand a light-shielding insulating layer laminated on another side of thebase substrate, wherein the base substrate has a structure in which thesame kind of metal layers are formed on respective sides of a resinfilm, where the structure of the base substrate is formed by laminatingmetal foils on the respective sides of the resin film via an adhesivelayer, the light-shielding insulating layer of the conductive sheet hasa surface having a surface resistivity of 1.0×10⁸ Ω/square or more, andthe conductive adhesive layer of the conductive sheet has a surfacehaving a surface resistivity of 500 mΩ/square or less, and theconductive sheet exhibits a shape retentivity property in that when theconductive sheet further comprises a release sheet on a side of theconductive adhesive layer, and when the conductive sheet is cut into asample strip with a width of 15 mm and a length of 50 mm and bent at 90°at a center of the sample strip on a side of the light-shieldinginsulating layer to form a shaped sample, the shaped sample retains itsshape for at least 10 seconds after the release sheet is peeled from thesample strip in a direction of 180°.
 19. An image display in which aportion to be electrically connected is disposed in a rough plane and isconnected by the conductive sheet according to claim
 18. 20. An imagedisplay in which portions to be electrically connected are disposed onrespective different planes and are connected by the conductive sheetaccording to claim
 18. 21. An image display comprising: a displayoperation panel in which a top electrode provided on an outer edge of asurface of the display operation panel and a back electrode provided onan outer edge of a back face are connected via the conductive sheetaccording to claim 18 that is disposed so as to surround the outer edgeof the display operation panel; and an image display panel that isoperated by the display operation panel.
 22. An image display in whichthe conductive sheet according to claim 18 is bonded to the imagedisplay so as to surround an outer edge of at least one constituentmember thereof.
 23. A conductive sheet comprising a base substrate, aconductive adhesive layer laminated on one side of the base substrateand a light-shielding insulating layer laminated on another side of thebase substrate, wherein the base substrate has a structure in which thesame kind of metal layers are formed on respective sides of a resinfilm, where the structure of the base substrate is formed by laminatingmetal foils on the respective sides of the resin film via an adhesivelayer, the light-shielding insulating layer of the conductive sheet hasa surface having a surface resistivity of 1.0×10⁸ Ω/square or more, andthe conductive adhesive layer of the conductive sheet has a surfacehaving a surface resistivity of 500 mΩ/square or less, and theconductive sheet exhibits a shape followability property in that whenthe conductive sheet further comprises a release sheet on a side of theconductive adhesive layer, and when the conductive sheet is cut into asample with a length of 15 mm and a width of 10 mm, an absence ofpeeling is observed in an environment of 80° C. and 95% relativehumidity for 72 hours after the release sheet is removed from the sampleand the sample is immediately bonded to a surface of an aluminum plate,the long side of the sample being bonded to the aluminum plate such thata portion with a thickness of 1 mm of the aluminum plate is surroundedand a 1-mm edge on a surface of the aluminum plate is covered and theremaining sample is bent at 90° and bonded to a back face of thealuminum plate.
 24. An image display in which a portion to beelectrically connected is disposed in a rough plane and is connected bythe conductive sheet according to claim
 23. 25. An image display inwhich portions to be electrically connected are disposed on respectivedifferent planes and are connected by the conductive sheet according toclaim
 23. 26. An image display comprising: a display operation panel inwhich a top electrode provided on an outer edge of a surface of thedisplay operation panel and a back electrode provided on an outer edgeof a back face are connected via the conductive sheet according to claim23 that is disposed so as to surround the outer edge of the displayoperation panel; and an image display panel that is operated by thedisplay operation panel.
 27. An image display in which the conductivesheet according to claim 23 is bonded to the image display so as tosurround an outer edge of at least one constituent member thereof.